Before repairing injection molding machine, it is necessary to fully understand working principle of machine, such as electrical principle, hydraulic principle and mechanical principle. Secondly, we must follow four steps of ancients to see a doctor: look, smell, ask, and cut. Keep a clear head, don't be impatient, first find out which fault belongs to the electrical, hydraulic, and mechanical aspects. Simple distinction can be as follows:

 

1. If motor does not turn and makes an abnormal sound at the same time, immediately turn off emergency stop button, check whether fuse is blown or loose, and then check whether three-phase power supply of motor is normal;
2. Press motor start button, there is no possibility of button switch, loose wire of AC contactor, or action of thermal relay due to sound of motor;
3. Oil pump is stuck, causing motor not to rotate (motor makes some noise at this time);
4. If motor is burned out, repair it according to original specifications and find cause (such as phase failure, overload, bad contacts of AC relay, loose contacts of motor line, or unbalanced or unstable three-phase power supply voltage)

1. If solenoid coil of small pump solenoid relief valve or pressure proportional valve does not suck or internal valve core is stuck by debris, remove it for cleaning, and check whether solenoid coil is burnt, whether wiring is loose, or is in poor contact;
2. Oil pump is damaged, repair or replace oil pump
3. Oil level is too low, causing pump to suck empty
4. Is oil filter blocked?
5. Whether motor is reversed and commutated
6. There is air in oil pump, first deflate
7. Main valve core that controls relief valve of large pump is stuck, remove relief valve for cleaning.

1. Wiring of safety door travel switch is loose or damaged, and safety door travel is not pressed down, check SQ1, SQ2, SQ3
2. SQ4 travel switch is closed
3. Clamping solenoid valve valve is stuck or solenoid valve socket is loose
4. Formation switch of thimble retracting is not closed
5. No system pressure: repair according to item (2)

1. Injection pressure is low and speed is too slow: increase injection pressure and increase injection speed
2. Bottom of plastic heating temperature: increase temperature
3. Nozzle is blocked, remove it for heating and cleaning
4. Injection time is too short
5. Injection solenoid valve is stuck
6. Injection solenoid valve shall not be electrified. Check for electrical reasons

 

1. Pre-plastic termination travel switch has been closed, and striker of travel switch is opened.
2. One-way throttle valve closed
3. If material temperature is too low, increase material temperature
4. Pre-plastic solenoid valve is stuck, remove it for cleaning
5. Pre-molding pressure is too low, increase pre-molding pressure
6. Foreign body enters screw and screw is stuck. Disassemble screw cleaning, barrel cleaning
7. Hydraulic motor is broken and bearing is stuck

1. Back pressure is too high
2. Cooling water from feeding port is insufficient, and material in feeding port is "bridged"; adjust water volume and take out plastic block with sticky structure
3. Lack of material, feeding
4. Screw is broken
5. Back pressure is adjusted too high, and back pressure is lowered

1. System pressure is over-regulated
2. Tie rod nut of rear formwork is stuck due to impurities or lack of lubricating oil; clean tie rod nut, repair it, pay attention to same axial clearance of four nuts when installing, and then add lubricating grease
3. Mold adjusting solenoid valve is stuck or socket is loose: check and repair
4. Hydraulic motor of mold adjustment is damaged, repair or replace

1. Pressure of oil pump is too high: appropriately reduce working pressure according to plastic molding process
2. Insufficient oil in fuel tank: add enough hydraulic oil
3. Oil cooler has been used for a long time, it is full of scale, and cooling effect is poor. Clean cooler
4. Cooling water flow is not large enough, or cooling water temperature is not low enough

Semi-automatic operation is that safety door is opened, travel switch is closed, and a signal is sent to make machine start semi-automatic action, and then mold is closed. After hitting SQ4 travel switch, mold is closed, and injection starts at the same time. Injection time relay starts timing. Start pre-molding, after encountering limit switch at the end of pre-molding, start to prevent flow, after encountering limit switch of anti-flow, cooling time relay starts timing, after time is up, mold opening action is performed, then mold is opened, and mold opening is terminated. After travel switch, do ejection action, after touching ejection termination limit switch, do ejection action, after touching ejection termination travel, wait for safety door to be opened, so that work is repeated.
It can be seen from above that if manual operation is normal, it is generally caused by failure of travel switch and time relay to send a signal. According to failure of semi-automatic action in the stage of mechanical cycle, find out corresponding control components according to electrical and hydraulic schematic diagrams, check and solve them.